html,
body,
.main {
  height: 100%;
}

.main {
  display: flex;
  flex-direction: column;
}

.main .topbar {
  width: 100%;
  height: 50px;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 100;
}

.main .box {
  flex: 1;
  padding-top: 50px;
}
